1. Field of the Invention
The subject invention generally relates to a hyperdispersant. More specifically, the hyperdispersant of the subject invention is useful in fluorocarbon coating compositions.
2. Description of the Related Art
Fluorocarbon resins, such as polyvinylidene fluoride (PVDF), are useful in formulating coatings with excellent weathering resistance. It is common to add binder resins, or hyperdispersants, to fluorocarbon coating compositions because fluorocarbon resins have poor rheology and pigment wetting characteristics. To achieve optimal weathering and chemical resistance, high fluorocarbon resin content is desired in the coating compositions. Many coating applications call for coating compositions having 70 weight percent or more fluorocarbon resins and the remainder is the binder resin. Coating compositions containing fluorocarbon resins, particularly PVDF, and binder resins tend to have relatively high viscosities. For some coating applications, particularly coil coating applications, it would be desirable to have high fluorocarbon resin content in conjunction with the binder resin, but with lower viscosity than is currently possible with the related art compositions.
Typical binder resins that have been previously utilized with fluorocarbon coating compositions have hydroxyl and amine functionality because of the improved mechanical and chemical resistance that results from such functionality. However, the source of such binder resins and hyperdispersants has previously been limited. The primary hyperdispersant is 3-(2-methacryloxyethyl)-2,2-spirocyclohexyl oxazolidine (MESO) and the MESO monomers are becoming increasingly difficult and/or more expensive to obtain due to the high cost of manufacturing.
Because MESO monomers are difficult to obtain, some related art methods have manipulated the binder resin during formation. For example, the binder resins have been polymerized from acrylic acids and acrylic esters having no additional functionality, acrylic acids, and acrylic esters having additional functionality, and an acryloxyalkyl oxazolidine. The functional acrylic acid/esters provide sites for cross-linking with cross-linking agents. The acryloxyalkyl oxazolidine reduces the viscosity of the fluorocarbon resin and acrylic resin dispersion. Other attempts to lower viscosity of the acrylic resin have included polymerizing and/or reacting the acrylic resin with polyimides, amino groups, epoxy groups, and the like. However, these modified acrylic resins do not perform as well as acrylic resins modified with MESO.
A co-pending patent application, which is commonly owned by the Assignee of the subject invention, described a novel method of formulating the binder resin from commercially available components such that the binder resin performed as well as, if not better, than the acrylic resins modified with MESO. In the co-pending patent application, a first component was an acrylic resin having an epoxy group that was reacted with an amino compound having a primary or secondary amine to open the epoxy group. Even though such a binder resin performed well, it was discovered that during commercial utilization contaminates would react with (or prevent reaction of) the epoxy group leaving limited sites available for the amine group to react. Thus, the binder resin did not as effectively disperse the fluorocarbon resin because the binder resin had limited functionality.
Accordingly, it would advantageous to provide a hyperdispersant that adequately lowers viscosity and that provides desired pigment wetting characteristics when incorporated into a coating composition. Further, it would be advantageous to provide a method of forming the hyperdispersant from monomers and starting components that are commercially available and that are relatively inexpensive such that manufacturing coating compositions that include the hyperdispersant is not cost prohibitive.